Method and apparatus for the continuous expansion of tubular objects



Sept. 3, 1957 D. T. MlLNE 2,804,642 METHOD AND APPARATUS FOR THE CONTINUOUS EXPANSION OF TUBULAR OBJECTS Filed June 2, 1953 METHOD AND APPARATUS FOR THE CONTINU- OUS EXPANSIDN F TUBULAR OBJECTS David T. Milne, Fredericksburg, Va., assignor to American Viscose Corporation, Philadelphia, Pa, a corporation of Delaware Application June 2, 1953, Serial No. 359,134

11 Claims. (Cl. 18-1) The present invention relates to the manufacture of tubular products such as artificial casings for meat products, bands for bottlenecks and similar articles. In particular the invention relates to novel methods and apparatus for producing tubular products of definite and uniform diameter.

In the manufacture of the various well-known types of cellulosic artificial casings, such as those fabricated from cellulose and derivatives thereof, for example, viscose, cellulose acetate, hydroxyeth'yl cellulose, nitrocellulose, cupramrnonium cellulose, etc., it is desirable to maintain uniformity of size, strength, shape, and appearance.

In the past it has been customary to control the diameter of the tubular material by inflating the tubes during their production with a suitable gas, such as air. By controlling the pressure of the gas delivered to the interior of the tube, it was possible to harden or fix the casing while in an inflated condition. With this procedure, however, considerable diflrculty has been experienced in sufliciently obtaining and maintaining the desired uniform density and wall thickness of the tubular material during the hardening process when the tube is relatively plastic and pliable. Difiiculty was also encountered in maintaining a continuously moving tube at exactly the desired diameter. Also the tubing, when inflated, frequently lost its desired diameter due to small holes present in the wall of the tubing due to the rupture of weak spots within the tubing wall, the weak spots being caused by the presence of air bubbles in the spinning dope.

It is an object of the present invention to provide a method and apparatus for producing continuous tubular material exhibiting definite and uniform diameter which overcome the above objections wherein the diameter of the continuously traveling tubing may be easily controlled even if small holes are present in the tubing wall.

Another object of the invention is to provide a method for controlling the diameter of continuous traveling regenerated cellulose tubing while passing initially flattened tubing through a liquid treating bath and then expanding the tubing with the use of a treating liquid.

An additional object is to provide a method for controlling the diameter of the tubing by varying the level of the liquid treating bath with respect to the height of a liquid column within the tube.

Another object of the invention is to provide in apparatus for producing continuous tubing exhibiting definite and uniform diameters, means for varying the liquid level of the treating bath.

Other objects of the invention will be apparent from the following description and drawings in which:

Figure l is a vertical section 'of one embodiment of the invention, and V Figure 2 is a vertical section of another embodiment of the invention.

In general the improved method of the present inven- 2,864,642 Patented Sept. 3, 1957 ice tion includes introducing extruded plastic tubing into a liquid treating chamber, passing the tubing between a pair of juxtaposed nip rolls adjacent one end of the liquid treating chamber and withdrawing the tubing from the chamber between a second pair of juxtaposed nip rolls. The proper amount of liquid is introduced into the interior of the tubing to open and to maintain the tubular material in an expanded condition as it travels through the bath. The diameter of the tubular material is then controlled by regulating the height of the treating liquid in the chamber with respect to the height of the liquid within the tube. It has been found that the desired expansion, contraction and other important characteristics of the finished tubular material may be accurately and readily achieved in this manner.

The invention also provides apparatus for introducing an initially flattened, extruded tube into a liquid treating bath, including means for conveying a portion of the tube in expanded condition through the bath and means for varying the liquid level of the treating bath.

As will be more apparent hereinafter any conventional and suitable solution or liquid may be supplied to the chamber during the processing of the tubular material therein. For example, there may be used a regenerative solution of dilute sulfuric acid and sodium sulfate, a bleach solution of hypochlorous acid, a desulphurizing solution of sodium sulfide, an aqueous wash or any other suitable solution. The liquid which is supplied to the interior of the tubular material may be the same as that which is supplied to the treating chamber. However, a relatively inexpensive liquid which is immiscible with the treating liquid may be introduced into the tube so that it can be readily recovered should the tubing become ruptured to such an extent that the liquid within the tubing passes into the treating bath.

The structural details of one embodiment of the present invention are shown in Figure l of the drawing. As

illustrated therein, the flattened tubular material 1 is.

conducted from any suitable type of tube extrusion apparatus 2 about the guide roll 3, into the liquid treating tank 4, about guide rolls 5 and 6, and then between the lower pair of nip rolls 7 and 8. After the tank 4 is filled with treating liquid and before the tube 1 is fed through nip rolls 9 and 10, an amount of a suitable liquid is introduced from an external source into the bore of the tube 1 byforcing the liquid through any suitable opening such as a slit made in the upper portion of the tube. When the tube is filled to a level substantially commensurate with the level of the treating bath, it is then fed between nip rolls 9 and 10. However, the tube 1 may be fed through the rolls 9 and 10 which rolls may be then spread apart to permit introduction of liquid therebetween and into the bore of the tube after which the nip rolls 9 and 10 are brought together. After the tubing leaves nip rolls 9 and 10, it passes upwardly to a further processing station, or collection station, not shown in the drawings. The portion of the tube 1 between the two sets of squeeze rolls thereby assumes an expanded circular form indicated at 12 which form is retained as the tube continuously passes through the treating bath 11. The nip rolls 7, 8, and 9, 10 are preferably driven at predetermined independently controlled rates on their respective shafts 7a, 8a, 9a, and 10a in any suitable manner. i

The diameter of the tubing 1 is controlled by raising, lowering or maintaining constant the level of the treating bath with reference to the level of the liquid column within the tube. As the treating bath level is lowered, there results a corresponding decrease in the bath pressure exerted upon the external periphery of the expanded tube portion 12 and the liquid column therewithin. As a consequence of such pressure decrease, the liquid pressure exerted upon the inner surface of the tube portion 12 by the column of liquid within the tube bore is opposed by less bath pressure than before the bath level was lowered and, therefore, the internal liquid pressure'further expands the tube portion 12 to effect an increase in the diameter thereof. This action is accompanied by a lowering of the level and liquid pressure of the liquid column within the bore of the tubing. As the bath level is raised, there results a corresponding increasein the bath pressure exerted upon the wall of the expanded tube portion 12 and the liquid column therewithin. As a consequence of such pressure increase, the liquid pressure exerted upon the wall ofthe tube portion 12:by,the column of liquid within the tubing. bore is opposed by greater bath pressure than before the bath level was raised which effects a decrease in the diameter of the expanded tube portion 12. This action is accompanied by'raising of the level and liquid pressure of the liquid column within the tubing bore. To control the bath level and co'nsequently the external liquid pressure exerted upon the expanded tube portion 12 and the liquidcolumn therewithin controlled overflow systemand azsupply system indicated generally by reference numerals,13. and 1-7 respectively are provided. The overflow system: comprises three spigots or valves.14 positioned at different heights exteriorly of the chamber 4 to control .the withdrawal or overflow of treating liquid from bath 11. The liquid flowing through valves 14 passes into drain 15 and is thereby conveyed to the reservoir 16. By openingor closing. the valves 14, the level of the liquid within .the

chamber 4 may be closely regulated as desired. Toraise' the level of the treating liquid within the chamber, liquid may be pumped from container 16 into the liquid treating. chamber 4. The treating liquid which is collected in the container 16 is preferably returned to the chamber by the conventional pump 18 positioned'in the conduit 19 which extends from the-container lG to the top of the treating tank 4-to empty into the tank.

Additional supply liquid for the treating chamber may also be fed. to reservoir 16 from container 16a. When the tube 1 leaves the treating bath 11, it is completely set up or coagulated and it may then be dried or subjected to other processing steps such as cutting, slitting, etc.

By regulating the valves 14 and the amount of liquid introduced into the liquid chamber through conduit 19,

the relative height of the treating liquid in the tankrnay be varied. or maintained with respect to the height of the liquid column within the expanded tube portion 12. Moreover as the level of the treating liquid is varied, the external fluid pressure exerted upon the expanded tube portion 12 is varied proportionately so as to effect control of the expansion and contraction characteristics of the tube 21 between nip-rolls 29 and 30, the tube is slit to force treating liquid into the tube 21 to form an :ex-

panded tube portion 31 within the bath 27, after which 4 29, and 30 are mounted on driven shafts 25a, 26a, 29a, and 30a and may be driven by any suitable driving means.

By reversing the direction of rotation of the nip-rolls, the tubing 21 may travel through the bath 27 in a downward direction. The tube 21 may be fed into the treating bath 27 from the top of tank 28, through nip-rolls 29 and 30, and then proceed downwardly to leave the bath 27 between nip-rolls 25 and 26 and through opening 23 in the overflow container 24. When using this procedure, the extruded tube 21 is fed between nip-rolls 29 and 30 and then brought to the surface of the bath 27. After a suitable amount of the tubing enters the bath, the tube bore is filled with treating liquid. The free end of the tube 21 is then clamped to prevent escape of liquid and the tube is allowed to descend to the bottom of the bath to be fed between nip-rolls 25 and 26, through the overflow container opening 23, and to any additional processing station.

By varying or maintainingconstant the level 'of bath 27 with reference to the height of the liquid within the expanded tube portion 31, the diameter of the tube 21 may be accurately controlled. As the treating bath level is lowered, there results a corresponding decrease in the bath pressure exerted upon the external periphery of the expanded tube portion 31 and the liquid column therewithin. As a consequence of such pressure decrease, the liquid pressure exerted upon the internal periphery 'of the tube portion 31 by the column of liquid within the tube bore is opposed by less bath pressure than before the bath level was lowered and therefore the iinternal liquid pressure further expands the tube portion 31 to effect an increase in the'diameter of tube portion 31. This action is accompanied by a lowering of the level and liquid pressure of the liquid column within the bore of the tubing. As the bath level is raised, there results a corresponding increase in the bath pressure exerted upon the periphery of the expanded tube portion 31 and the-liquid column therewithin. As a consequence of such pressure increase, the liquid pressure exerted upon the internal periphery of the tube portion 31 by the column of liquid within the tubing bore is opposed by greater bath pressure than before the bath level was raised which effects a decrease in the diameter of the expanded tube portion 31. This action is accompanied by raising of the level and liquid pressure of the liquid column within the tubing bore. To control the bath level and consequently the external liquid pressure exerted upon the expanded tube portion 31, a bath overflow system and a bath supply system indicated generally by reference numerals 32 and 33, respectively, are provided. The overflow system comprises three spigots or valves 34 positioned at different heights exteriorly of the chamber 28 to control the withdrawal or overflow of treating liquid from bath 27. The liquid flowing through valves 34 passes into drain 35 and is thereby conveyed to the overflow container 24 secured in any suitable manner to the lower extremity of the tank 28. By opening or closing one or more valves 34, the liquid level in the chamber or tank 28 may be closely regulated. The treating liquid which is collected in the container 24 may be returned to the liquid replenishing source 40 and to the chamber- 28 to raise the level of the liquid therein by the conventional pumping device or the like 41 positioned below tank 24, through the pipes or conduits 42 which are preferably secured to the container or tank 28 in any suitable manner.

As will be more apparent hereinafter the annular centrally apertured ridge or the like 36 which extends upintroduction of treating liquid within the tube 21 after tube portion 31. The tube 21 then passes upwardly out' of-the bath to an additional processing or collecting station not shown irithe drawings; The nip-re1ls-25";"26,"

wardly from the bottom surface of the container 24 is adapted to permit the continuously advancing material to pass upwardly from the extrusion apparatus 22' through the container 24 and between the pair of juxtaposed niprolls 25 and 26 positioned in the slot of opening 37 in the bottom .portion of the tank 28. The flexible shoe members 38an'd 39which may be constructed preferably from any suitable resilient material such as rubber or the like are adapted to be secured to the flanged end portions of the slot 37 and are curvilinearly contoured so as to closely follow the periphery of the nip-rolls 25 and 26 and yet not impede or interfere with the rotation of the same on their respective shafts. The two pair of nip-rolls 25 and 26, and 29 and 30 are preferably driven at the same rate of speed. When, however, the overall length of the tubular portion 31 varies due to changes in the degree of expansion thereof, it is to be understood that the rate of either pair of nip-rolls is variable and/ or adjustable with respect to the other pair of nip-rolls so that the tubular material continuously follows a substantially linear path between the said pairs of nip-rolls.

The embodiment as shown in Figure l is preferred when the diameter of the tube is to be greatly enlarged. As seen in Figure 1, the tube travels the depth of the treating bath in a flattened condition which tends to set up or coagulate the outer portions of the tube periphery which action makes the tube stronger and thus tends to prevent rupture of the tube after liquid is introduced with in the bore of the tube.

The embodiment as shown in Figure 2 is preferred when the diameter of the extruded tube is to be only slightly enlarged or decreased. As seen in Figure 2, the tube is expanded as soon as it enters the treating bath, thus affording no chance to set up or coagulate the outer portions of the tube periphery.

The invention as disclosed provides a system for accurately regulating the tube diameter. The level of the bath need only be raised or lowered slightly to effect a change in the diameter of the expanded portion of the tube.

While preferred embodiments of the invention have been disclosed, the description is intended to be illustrative only and it is to be understood that changes and variations may be made without departing from the spirit and scope of the invention as defined by the appended claims. 1

I claim:

1. A method of setting the diameter of continuously traveling plastic tubing comprising the steps of continuously conducting the tubing through a liquid treating bath, constricting the tubing within the bath, supplying a liquid to the interior of the tubing to form a liquid column within the tubing interior adjacent the constriction, constricting the tubing again along the liquid filled portion of the tubing to form an expanded portion in the tubing within the bath, and adjusting the level of the treating bath to fix, as described, the diameter of the liquid column within the tubing through changes in external pressure exerted upon the liquid column.

2. A method of setting the diameter of continuously traveling plastic tubing according to claim 1, characterized in that the plastic tubing comprises cellulosic tubing.

3. A method of setting the diameter of continuously traveling plastic tubing according to claim 1, characterized in that the liquid within the tubing comprises a liquid dissimilar to that of the treating bath.

4. A method of setting the diameter of continuously traveling regenerated cellulose tubing comprising the steps of continuously conducting cellulosic tubing through a regenerating bath, constricting the tubing within the bath, supplying a liquid to the interior of the tubing above the constriction to form a liquid column therein, constricting the tubing again above the first constriction and at a point adjacent and above the surface level of the bath to form an expanded portion in the tubing within the bath, and adjusting the level of the treating bath to fix, as desired, the diameter of the liquid column within the tubing through changes in external pressure exerted upon the liquid column.

5. A method of setting the diameter of continuously traveling regenerated cellulose tubing comprising the steps of continuously conducting extruded tubing through aregenerating bath, constricting the tubing within the bath, supplying a liquid to the interior of the tubing above the constricted point to form a liquid column therein, constricting the tubing again above the first constriction to form an expanded tube portion within the bath, and adjusting the level of the treating bath to fix, as desired, the diameter of the liquid column within the tubing through changes in external pressure exerted upon the liquid column.

6. A method of setting the diameter of continuously traveling plastic tubing comprising the steps of continuously conducting extruded tubing through a liquid treating bath, constricting the tubing within the bath, supplying a treating liquid to the interior of the tubing above the first constriction to form a liquid column therein, constricting the tubing again above the first constriction to form an expanded portion in the tubing Within the bath, and supplying additional treating liquid to the liquid bath to raise the level thereof to decrease the diameter of the liquid column within the tubing.

7. A method of setting the diameter of continuously traveling plastic tubing comprising the steps of conducting tubing through a liquid treating bath, constricting the tubing at a point within the bath, supplying a treating liquid to the interior of the tubing above the constriction to form a liquid column therein, constricting the tubing again above the first constriction to form an expanded portion in the tubing within the bath, and withdrawing treating liquid from the bath to lower the level thereof to increase the diameter of the liquid column within the tubing.

8. A method of setting the diameter of continuously traveling plastic tubing comprising the steps of continuously conducting extruded plastic tubing upwardly through a liquid treating bath, constricting the tubing at a point within the bath, supplyingv a liquid to the interior of the tubing above the constriction to form a liquid column therein, constricting the tubing again above the first constriction to form an expanded portion of the tubing within the bath, and adjusting the level of the treating bath to fix, as desired, the diameter of the liquid column within the tubing through changes in external pressure exerted upon the liquid column.

9. A method of setting the diameter of continuously traveling plastic tubing comprising the steps of continuously conducting extruded tubing downwardly through a liquid treating bath, constricting the tubing at a point within the bath, supplying a liquid to the interior of the tubing above the constriction to form a liquid column therein, constricting the tubing again above the first constriction to form an expanded portion in the tubing within the bath, and adjusting the level of the treating bath to fix, as desired, the diameter of the liquid column within the tubing through changes in external pressure exerted upon the liquid column.

10. Apparatus for setting the diameter of continuously traveling plastic tubing comprising a liquid container through which the tubing travels, means for introducing a liquid into the container, means for introducing liquid into the tubing interior to form a liquid column within the tubing, spaced apart tube constricting means supported Within the container, and means for adjusting the level of a liquid within the container while the tubing is traveling through the container to control the diameter of the liquid column formed within the tubing through changes in external liquid pressure exerted upon the liquid column.

11. Apparatus for setting the diameter of continuously traveling plastic tubing comprising a liquid container through which the tubing travels, means for introducing liquid into the container, means for introducing liquid into the tubing interior to form a liquid column Within the tubing, two pair of spaced apart nip rolls for the tubing which rolls are supported Within the container, and a Refrjhesr Cit'd in th file of this patent .U'NIT'EDSTATES PATENTS 1,6Q1;686" Henderson S pt. 28, 1926 2,401,773 Reighel et a1. June 11, 1946' Fo'REiGN PATENTS 524,757- Great Britain Aug. 14, 1940 i 

